The present invention relates to air-purifying filter cartridge assemblies and in particular to a combination filter/cartridge assembly containing a particulate filter media in series arrangement with a sorbent bed.
Cartridge filtering assemblies have been described previously in the art. One such assembly U.S. Pat. No. 4,548,626 to Ackley, discloses a combination of a radially pleated filter and a sorbent bed. This invention does not disclose a support between the round filter and the sorbent bed having radially directed vanes for distributing air over the sorbent bed. Thus, the airflow through the sorbent bed may be short circuited and cause premature exhaustion of the bed.
U.S. Pat. No. 6,044,842 to Pereira et al., discloses a gasketless adapter for fastening two filter elements to one another. However, the geometrical structure of the arrangement of the first and second does not allow for full utilization of the filtering capability and may cause excessive pressure drop.
U.S. Pat. No. 4,714,486 to Silverthorn, discloses a filter canister having a canister body with top and bottom parts sealed together, a filter for particulate material sealed into the top part and a separate sorbent cartridge fitted into the bottom part of the body. The design of the prior air filter cannister does not allow for uniform air distribution throughout the plenum chamber between the first and second filters which is an undesirable attribute of the design.
Therefore, as can be seen from the prior art patents, there is a need for a novel filter cartridge assembly which can be used with one or more filter assemblies and thus provide for structure bed integrity and for uniform distribution of air throughout the assembly.
The present invention meets the above-described need by providing a housing that combines with a particulate filter having an irregular shaped gas sorbent bed. Proper usage of the filter cartridge requires that the air passing through the filter be distributed uniformly over the sorbent bed. Thus, the filter cartridge directs the air radially over the surface of the sorbent bed utilizing the vane-like structures radiating out from the reticulated members. A multi-functional assembly located within the filter housing has been named a replendam. The term xe2x80x9creplendamxe2x80x9d is an acronym for an assembly which is a retention screen, a plenum chamber, and an adhesive barrier for a particulate filter.
As a retention screen, it provides stability to the sorbent bed to ensure individual grains of sorbent do not move or otherwise shift in the sorbent column. Errant settling or shifting of the sorbent changes the flow characteristics of the bed and effects essential residence time of the gases that the bed must absorb.
As a plenum chamber, it ensures that the face velocity across the sorbent bed is uniform.
As an adhesive barrier, it prevents migration of glue into the plenum when the particulate filter is potted in place. Since the immobilization screen must apply pressure evenly, the adhesive barrier must be designed to allow a cushion so the filter area under it is not crushed.
The foregoing and additional advantages and characterizing features of the present invention will become clearly apparent upon reading of the following detailed description together with the included drawings.